5. Discussion
The major findings of this study were as follows: 1) LBB capture threshold and pacing impedance were stable in the LBBAP population; 2) after LBBAP, QRS duration was significantly decreased; 3) learning curves for LBBAP procedures continued to improve with increasing operator experience; and 4) higher success rates and lower complication rates were achieved as experience increased.
Although HBP, which was first introduced by Deshmukh et al. in 2000,14 has been suggested as the ideal approach for physiological ventricular activation,15 wider clinical application of HBP is limited by several problems, including technical difficulties in identifying the precise location, variable success rates, and potential risk of premature battery depletion and lead revisions due to progressive increases in capture thresholds.15, 16
In this regard, LBBAP, which has a stable and lower capture threshold and a similarly paced QRS duration to HBP, has emerged as a new physiological conduction system modality.4, 5, 17LBBAP presents a simpler implant technique, shorter fluoroscopy, and shorter procedure time with a steeper learning curve compared to HBP; thus, LBBAP is now widely used as an alternative for conventional SP and considered as the first strategy for patients in whom a high burden of ventricular pacing is anticipated.5, 17 However, LBBAP has not yet reached widespread clinical use, and the main obstacle to widespread use is the limited array of available tools for LBBAP implantation. Although most cases of LBBAP have been exclusively performed using LLL with a fixed helix design and a pre-shaped sheath dedicated to this lead, LLL is not available to all manufacturers and implanters; thus there is a limited ability to offer LBBAP to all patients. Therefore, the ability to perform LBBAP with SDLs seems to encourage more implanters to attempt the LBBAP.
In this study, the plateau phase of the procedure time for LBBAP with SDL began from the 24th case, which is shorter than the previously reported learning curves ( 30–50 cases) of HBP and even LBBAP using LLL.18-20 In addition to the known advantages of the shorter learning curve of LBBAP compared to those of HBP, familiarity with SDL also contributed to a shorter learning curve than that of HBP.
These data are encouraging for centers considering the implementation of an LBBAP procedure, suggesting improved procedural results and procedural time with increased operator experience, which may lead to a more challenging procedure.